1. Field of the Invention
The present invention relates to laminography or computed tomography imaging and more particularly to locating the exact location of the source of the x-ray beam at a particular point in time.
2. Description of the Related Art
U.S. Pat. No. 6,628,745, issued to the present applicant, describes an x-ray source with an electron source that provides a pencil beam of electrons, a beam directing assembly that directs the pencil beam along a line that strikes a target. As the electron beam moves along the target, a traveling cone beam of x-rays is formed at the intersection point of the electron beam with the target. This cone beam can be collimated into a fan beam by use of a slit collimator adjacent to the target.
In order to use the system to form Laminography or computed tomography (CT) images, it is necessary to know with precision where the electron beam strikes the x-ray target at each instant of time so that the precise location of the source of the x-ray beam is known. Typically, the beam directing assembly is designed to move the beam in a linear and stable fashion over the target. However, there is always the possibility that the motion of the electron beam will drift and not be precisely at the required location for each period of time. This drift can be caused by, for example, external magnetic fields such the Earth's magnetic field, by a mechanical jarring of the system, or by temperature changes.